Haandrikman A J, van Leeuwen C, Kok J, Vos P, de Vos W M, Venema G
Department of Genetics, University of Groningen, Haren, The Netherlands.
Appl Environ Microbiol. 1990 Jun;56(6):1890-6. doi: 10.1128/aem.56.6.1890-1896.1990.
DNA segments of 809 and 808 nucleotides, with 18-base-pair terminal inverted repeats, are present on the proteinase plasmids pWV05 from Lactococcus lactis subsp. cremoris Wg2 and pSK111 from L. lactis subsp. cremoris SK11, respectively. These DNA segments are highly similar: 77% identical nucleotides and both contain an open reading frame that can encode a protein of 226 amino acids. Furthermore, both DNA segments are located downstream of the proteinase maturation gene prtM, but they differ individually in their orientation with respect to the prtM gene. On the basis of the striking similarity between ISS1, an 808-base-pair insertion sequence (IS) from L. lactis subsp. lactis ML3 lactose plasmid pSK08, and the DNA segments of pWV05 and pSK111, we propose that these DNA segments comprise IS elements. The IS elements from strains Wg2 and SK11 were named ISS1W and ISS1N, respectively. On pWV05, ISS1W is flanked on one side by only part of a second IS element, indicating that pWV05 evolved as a deletion derivative of a precursor plasmid that carried at least two IS elements.
来自乳酸乳球菌乳脂亚种Wg2的蛋白酶质粒pWV05和乳酸乳球菌乳脂亚种SK11的pSK111上，存在着809和808个核苷酸的DNA片段，带有18个碱基对的末端反向重复序列。这些DNA片段高度相似：核苷酸同一性为77%，且都含有一个开放阅读框，可编码一个226个氨基酸的蛋白质。此外，两个DNA片段都位于蛋白酶成熟基因prtM的下游，但它们相对于prtM基因的方向各自不同。基于来自乳酸乳球菌乳亚种ML3乳糖质粒pSK08的808个碱基对插入序列（IS）ISS1与pWV05和pSK111的DNA片段之间的显著相似性，我们提出这些DNA片段包含IS元件。来自菌株Wg2和SK11的IS元件分别命名为ISS1W和ISS1N。在pWV05上，ISS1W一侧仅由第二个IS元件的一部分侧翼，这表明pWV05是作为一个携带至少两个IS元件的前体质粒的缺失衍生物进化而来的。
